Understanding and Modeling the Aging Breast Microenvironment

Breast cancer incidence and mortality increase with age, yet the specific contributions of the aging tumor microenvironment (TME) to cancer progression remain poorly understood. This dissertation investigated how age-associated alterations in the breast extracellular matrix (ECM) influence cancer cell behaviors, with a particular focus on matrix-bound vesicles (MBVs), substrate stiffness, and engineered 3D age-mimetic breast cancer models that recapitulate the age-related TME alterations and facilitate aging cancer research and high-throughput age-specific drug screening. First, we identified and characterized MBVs in the breast ECM, demonstrating for the first time that MBVs from aged ECM promote cancer cell motility and invasiveness. Through proteomic and RNA analyses, we identified key microRNAs (miR-10b, miR-30e, and miR-210) and cytokines (e.g., adiponectin) that mediate these effects, suggesting MBVs as crucial regulators of age-related cancer progression. Second, we examined the role of substrate stiffness in modulating extracellular vesicle (EV) secretion by fibroblasts. Our findings reveal that increased stiffness alters EV size and composition via mechanotransduction pathways involving ROCK1, p53, and thioredoxin, highlighting the significance of mechanical cues in shaping the TME. To translate these insights into physiologically relevant models, we developed a 3D age-mimetic breast cancer model using aged and young mouse collagen matrices. This model successfully recapitulated age-associated changes in cancer invasiveness and enabled high-throughput drug screening, identifying FDA-approved drugs with age-specific efficacy. Furthermore, we introduced a hybrid aging model combining patient-derived organoids (PDOs) and decellularized ECM (dECM), providing a novel platform to investigate subtype- and age-specific breast cancer progression. Overall, this work enhances our understanding of the aging breast microenvironment and its impact on cancer progression and treatment response. These findings underscore the importance of age-specific therapeutic strategies and lay the foundation for the development of personalized approaches to breast cancer treatment in elderly patients.